Groups fly to the central atom at a slow pace

[phet-steele]

I'm not sure if this is a performance problem or if it is going to just be device specific or what, but as soon as I open the sim and try to add an atom or lone pair, they fly towards the central atom incredibly slow. This gif is real time:

Seen on Win 10 Chrome, for phetsims/QA/issues/642.

Troubleshooting Information

URL: https://phet-dev.colorado.edu/html/molecule-shapes/1.2.9-rc.1/phet/molecule-shapes_en_phet.html Version: 1.2.9-rc.1 2021-04-23 20:40:46 UTC Features missing: applicationcache, applicationcache, touch User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.93 Safari/537.36 Language: en-US Window: 1920x937 Pixel Ratio: 1/1 WebGL: WebGL 1.0 (OpenGL ES 2.0 Chromium) GLSL: WebGL GLSL ES 1.0 (OpenGL ES GLSL ES 1.0 Chromium) Vendor: WebKit (WebKit WebGL) Vertex: attribs: 16 varying: 30 uniform: 4096 Texture: size: 16384 imageUnits: 16 (vertex: 16, combined: 32) Max viewport: 32767x32767 OES_texture_float: true

[jonathanolson]

I'm not able to reproduce. Is there console output? I have no idea why it's running that slowly. Any idea how I'd be able to reproduce this?

[phet-steele]

I really have no clue myself.

• Nothing in the console
• DOES happen in the published version
• ?profiler shows no fps loss, and I am running at 300 fps
• The animation seems to speed up briefly if I resize my window while they are flying.

[jonathanolson]

I'm still unable to reproduce. @KatieWoe thoughts?

[KatieWoe]

Could this be similar to the issue we saw on Steele's device in States of Matter https://github.com/phetsims/states-of-matter/issues/354. It had to do with the refresh rate of his device. Could that be a cause?

[jonathanolson]

Yes, it looks similar! I reproduced with ?speed=0.1:

[jonathanolson]

This should be fixed. @KatieWoe can you verify that the speed seems about normal (with a normal framerate), but also that things function properly with lower speeds (e.g. ?speed=0.1).

[KatieWoe]

I was under the impression that ?speed=x was meant to change animation speed?

[jonathanolson]

I was under the impression that ?speed=x was meant to change animation speed?

It changes the timesteps the entire simulation is given, e.g. with ?speed=10, it will multiply each "elapsed time" by 10. So if your browser runs at 60fps (~0.016 seconds per frame), an elapsed time of 0.016s will be adjusted to 0.16s. This speeds up the sim, but also makes it mimic behavior as if it was running at 6fps.

So a ?speed=0.1 on a 60-fps device would effectively mimic behavior of 600fps.

[KatieWoe]

In that case this would affect most animations. I thought that was the intended behavior of that parameter.

[KatieWoe]

Discussed with @jonathanolson to clarify above. Looks good on master.

[jonathanolson]

Thanks!